Chlorogenic acid(5-CQA),neochlorogenic acid(3-CQA),and cryptochlorogenic acid(4-CQA),usually simultaneously exist in many traditional Chinese medicines(TCMs).However,insufficient attentions have been paid to the compa...Chlorogenic acid(5-CQA),neochlorogenic acid(3-CQA),and cryptochlorogenic acid(4-CQA),usually simultaneously exist in many traditional Chinese medicines(TCMs).However,insufficient attentions have been paid to the comparative metabolism study on these three isomeric constituents with similar effects on anti-inflammation until now.In this study,a novel strategy was established to perform comparative analysis of their metabolic fates in rats and elucidate the pharmacological mechanism of antiinflammation.Firstly,diagnostic product ions(DPIs)deduced from the representative reference standards were adopted to rapidly screen and characterize the metabolites in rat plasma,urine and faeces using UHPLC-Q-TOF MS.Subsequently,Network pharmacology was utilized to elucidate their anti-inflammatory mechanism.Consequently,a total of 73 metabolites were detected and characterized,including 50,47 and 43 metabolites for 5-CQA,4-CQA and 3-CQA,orderly.Moreover,the network pharmacology study indicated that these three isomeric constituents and their major metabolites with similar in vivo metabolic pathways exerted anti-inflammatory effects through co-owned 20 biological processes,which involved 10 major signal pathways and 159 potential targets.Our study shed light on the similarities and differences of the metabolic profiling and anti-inflammatory activity among these three isomeric constituents and set an example for the further researches on the active mechanism of isomeric constituents existing in TCMs based on comparative metabolism study.展开更多
Recent fission experiment data provide interesting structure information for neutron-rich nuclei in the mass A ～ 160 region. We apply the projected shell model to study the strongly-deformed, neutron-rich Sm isotopes...Recent fission experiment data provide interesting structure information for neutron-rich nuclei in the mass A ～ 160 region. We apply the projected shell model to study the strongly-deformed, neutron-rich Sm isotopes. We perform calculations for rotational bands up to spin I = 20 (29/2) for even-even (odd-neutron) Sm isotopes, and analyze the band structure of low-lying states with quasiparticle excitations. Emphasis is given to rotational bands based on one-quasiparticle (1-qp) configurations in the odd-mass 159Sm. The 159 Sm result is discussed together with those of the even-even isotopes 158,160Sm. New bands in 159Sm based on neutron 1-qp 1/2 and 5/2+ configurations are predicted. Electromagnetic transition probabilities are discussed.展开更多
The concentrations of 16 polycyclic aromatic hydrocarbons（PAHs） were determined in surface sediment samples from nine sites located at the Iguau River Basin in the Metropolitan Region of Curitiba,Brazil to evaluate ...The concentrations of 16 polycyclic aromatic hydrocarbons（PAHs） were determined in surface sediment samples from nine sites located at the Iguau River Basin in the Metropolitan Region of Curitiba,Brazil to evaluate their distribution and sources.The total concentration of the PAHs was greater for sediments from highly urbanized areas,while the sediments from the Iraí Environmental Protection Area（Iraí EPA） showed significantly low concentrations.The sediments from the Iguau and Barigui rivers were classified as highly contaminated,while those from the Cercado and Curralinho rivers were classified as moderately contaminated.The predominance of PAHs containing two to four aromatic rings in most of the samples suggested the direct input of raw sewage into the water resources evaluated.Benzo[g,h,i]perylene,dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene were predominant in sediments from the areas under the greatest urban and industrial development.The correlation between thermodynamic stability and the kinetics of evolution presented by the isomeric pairs indicated that combustion is the predominant source of PAHs in the sediments because the combustion of fossil fuels affected most of the points evaluated,followed by combustion of biomass and eventually combustion of oil product inputs.In general,the results showed that areas under strong urban influence,as well as the Iraí EPA,receive contributions of PAHs from similar sources.展开更多
Two isomeric metal-organic frameworks(MOFs) with 2-dimensional(2D) and 3-dimensional(3D) topologies both comprised of Cu(Ⅱ) and OTf(OTf = trifluoromethanesulfonate) ions were synthesized and characterized.The CO_2,CH...Two isomeric metal-organic frameworks(MOFs) with 2-dimensional(2D) and 3-dimensional(3D) topologies both comprised of Cu(Ⅱ) and OTf(OTf = trifluoromethanesulfonate) ions were synthesized and characterized.The CO_2,CH_4 and N_2 adsorption properties of the two isomeric MOFs were investigated from 263 K to 298 K at0.1 MPa.The results showed that the 2D MOF exhibited a higher selectivity for CO_2 from CO_2/CH_4 and CH_4from CH_4/N_2 compared to the 3D MOF,even though it possessed a lower surface area and pore volume.The higher adsorption heats of gases on the 2D MOF inferred the strong adsorption potential energy in the layered MOFs.Dynamic separation experiments using CO_2/CH_4 and CH_4/N_2 mixtures on the two MOFs proved that the2 D MOF had a longer elution time than the 3D MOF as well as better separation abilities.展开更多
Isomerism is an essential and widespread phenomenon in organic chemistry but rarely observed in covalent organic frameworks(COFs),a novel class of crystalline porous organic polymers with versatile applications.Herein...Isomerism is an essential and widespread phenomenon in organic chemistry but rarely observed in covalent organic frameworks(COFs),a novel class of crystalline porous organic polymers with versatile applications.Herein,we give an account of the first example of a controllable synthesis of constitutional isomers of a COF.The two isomers exhibited marked differences in their gas/vapor adsorption behaviors and chemical stability in various solvents.Furthermore,structure transformation from one isomer to the other was realized.This work not only paves the way for rational design and synthesis of COF isomers but also provides a vivid example of structure–property relationship in crystalline porous polymers.展开更多
The ^(nat)Mo(γ,xnp)^(95m,g)Nb photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40.The experiment was performed using the activation and off-line γ-ray spectrometric ...The ^(nat)Mo(γ,xnp)^(95m,g)Nb photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40.The experiment was performed using the activation and off-line γ-ray spectrometric technique.The experimental isomeric yield ratio(IR) was determined for the reaction products ^(95m,g)Nb at the bremsstrahlung end-point energy E_(γmax) range of 38-93 MeV.The obtained values of IR are in satisfactory agreement with the results of other studies and extend the range of previously known data.The theoretical values of the yields Y_(m,g)(E_(γmax)) and the IR for the isomeric pair ^(95m,g)Nb from the ^(nat)Mo(γ,xnp) reaction were calculated using the partial cross-sections σ(E) from the TALYS1.95 code for six different level density models.For the investigated range of E_(γmax),the theoretical dependence of IR on energy was confirmed-the IR smoothly increases with increasing energy.The comparison showed a noticeable difference(more than 3.85 times) in the experimental IR relative to all theoretical estimates.展开更多
We present here a series of perylene diimide(PDI)based isomeric conjugated polymers for the application as efficient electron acceptors in all-polymer solar cells(all-PSCs).By copolymerizing PDI monomers with 1,4-diet...We present here a series of perylene diimide(PDI)based isomeric conjugated polymers for the application as efficient electron acceptors in all-polymer solar cells(all-PSCs).By copolymerizing PDI monomers with 1,4-diethynylbenzene(para-linkage)and 1,3-diethynylbenzene(meta-linkage),isomeric PDI based conjugated polymers with parallel and non-parallel PDI units inside backbones were obtained.It was found that para-linked conjugated polymer(PA)showed better solubility,strongerπ-πstacking,more favorable blend morphology,and better photovoltaic performance than those of meta-linked conjugated polymers(PM)did.Device based on PTB7-Th:PA(PTB7-Th:poly{4,8-bis[5-(2-ethylhexyl)-thiophen-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophene-4,6-diyl})showed significantly enhanced photovoltaic performance than that of PTB7-Th:MA(3.29%versus 0.92%).Moreover,the photovoltaic performance of these polymeric acceptors could be further improved via a terpolymeric strategy.By copolymerizing a small amount of meta-linkages into PA,the optimized terpolymeric acceptors enabled to enhance photovoltaic performance with improved the short-circuit current density(Jsc)and fill factor(FF),resulting in an improved power conversion efficiency(PCE)of 4.03%.展开更多
The yields of photonuclear reactions in the 107Ag,113In,and 115In nuclei were measured.Monte Carlo simulations were performed using the Geant4 code,and the results were compared with the experimental values.The isomer...The yields of photonuclear reactions in the 107Ag,113In,and 115In nuclei were measured.Monte Carlo simulations were performed using the Geant4 code,and the results were compared with the experimental values.The isomeric ratios of the yields in the reactions 107Ag(γ,n)106m,gAg and 113In(γ,m)112m,gIn were determined,and the cross sections for the reactions 107Ag(γ,n)106gAg and 107Ag(γ,2n)105Ag at an energy of 20 MeV were calculated based on the experimental data.展开更多
Two new isomeric Au complexes, Au（PPh3）（bmt）, have been synthesized via the reaction of Au（PPh3）CI with 2-benzimidazolethiol （Hbmt） in dichloromethane （CH2Cl2） solution. Their crystal structures were determi...Two new isomeric Au complexes, Au（PPh3）（bmt）, have been synthesized via the reaction of Au（PPh3）CI with 2-benzimidazolethiol （Hbmt） in dichloromethane （CH2Cl2） solution. Their crystal structures were determined by elemental analysis and single-crystal X-ray diffraction studies. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 19.589（2）, b = 21.1368（15）, c = 23.424（2） A, β = 108.346（4）°, V= 9206.1（14） A3, Mr = 1216.85, Dc = 1.756 g/cm3, μ = 6.566 mm^-1, F（000） = 4704, Z = 8, the final R = 0.0563 and wR = 0.1028 for 8125 reflections with I 〉 2σ（I）. Complex 2 crystallizes in the monoclinic system, space group P21/n with a = 9.627（3）, b = 21.384（8）, c = 22.308（8） A, β = 92.068（6）°, V= 4590（3） A3, Mr = 1216.85, Dc = 1.761 g/cms, μ = 6.585 mm^-1, F（000） = 2352, Z = 4, the final R = 0.0500 and wR = 0.0883 for 10477 reflections with I 〉 2σ（i）. X-ray diffraction studies reveal that complexes 1 and 2 both feature a 1D chain along the a axis.展开更多
The chlorocarbenoid , CHCl2Li , was studied by means of ab initio molecular or- bital theory. Three equilibrium structures and two isomerization transition states were located. The calculations showed that the three-m...The chlorocarbenoid , CHCl2Li , was studied by means of ab initio molecular or- bital theory. Three equilibrium structures and two isomerization transition states were located. The calculations showed that the three-membered ring structure is the most stable. The 'classical tetrahedral' structure is not the local minimum on the potential energy surface.展开更多
The isomeric structures, isomerization and decomposition of silylenoids H(2)SiMX (MX=KF, KCl, LiBr, NaBr and KBr) have been investigated by ab initio molecular orbital theory. These silylenoids have four kinds of very...The isomeric structures, isomerization and decomposition of silylenoids H(2)SiMX (MX=KF, KCl, LiBr, NaBr and KBr) have been investigated by ab initio molecular orbital theory. These silylenoids have four kinds of very similar equilibrium structures. The three-membered ring and p-complex structures should be stable and experimentally detectable. The lifetime of sigma-complex and tetrahedral structures would be very short and experimentally undetectable.展开更多
An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly（α-methylstyrene）（PαMS） chains is studied, in which the effect of large side group...An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly（α-methylstyrene）（PαMS） chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.展开更多
Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majora...Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction. Under certain conditions, they become the yrast state or yrare state. These states are difficult to decay and become very stable. This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.展开更多
A lead-shielded HPGe detector and offlineγ-ray spectra of the residual product were used to measure the cross section(CS)and ratios of isomeric CS(σm/σg)in^(134)Xe(n,2n)^(133m),gXe reactions at different energies(1...A lead-shielded HPGe detector and offlineγ-ray spectra of the residual product were used to measure the cross section(CS)and ratios of isomeric CS(σm/σg)in^(134)Xe(n,2n)^(133m),gXe reactions at different energies(13.5 MeV,13.8 MeV,14.1 MeV,14.4 MeV,14.8 MeV)relative to the^(93)Nb(n,2n)^(92)mNb reaction CS.The target was high-purity natural Xe gas under high pressure.The T(d,n)4He reaction produces neutrons.TALYS code(version 1.95)for nuclear reactions was used for calculations,with default parameters and nuclear level density models.The uncertainties in the measured CS data were thoroughly analyzed using the covariance analysis method.The results were compared with theoretical values,evaluation data,and previous experimental findings.CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5 MeV,13.8 MeV,and 14.1 MeV neutron energies are reported for the first time.This research advances our knowledge of pre-equilibrium emission in the(n,2n)reaction channel by resolving inconsistencies in the Xe data.展开更多
A new value for the emission probability of 137.144 keV γ-rays from 186gRe decay is recommended to be （9.47±0.03）/%. Using this value the measured cross sections for 187Re（n,2n）186mRe and 187Re（n,2n）186gRe...A new value for the emission probability of 137.144 keV γ-rays from 186gRe decay is recommended to be （9.47±0.03）/%. Using this value the measured cross sections for 187Re（n,2n）186mRe and 187Re（n,2n）186gRe reactions around 14 MeV are analyzed, and the cross section for187Ke（n,2n）186m＋gRe reaction at 14.g MeV is （2213=k116） mb. The UNF code was adopted to calculate the cross sections for the 187Re（n,2n）186m＋gRe reaction below 20 MeV, fitting to the value （2213±116） mb at 14.8 MeV using a set of optimum neutron optical potential parameters which were obtained based on the relevant experimental data of rhenium. The isomeric cross section ratio for the 187Re（n,2n）186m,gRe reaction was analyzed using the V-H method based on nuclear statistical theory. Combining these calculated results, the excitation functions for the 187Re（n,2n）lS6mRe and 187Re（n,2n）186gRe reactions were obtained. The obtained results are in good agreement with the available experimental data.展开更多
基金supported by the Young and Creative Team for Talent Introduction of Shandong Province(No.10073004)Binzhou Medical University Scientific Research Fund for High-level Talents(Nos.2019KYQD06 and BY2018KYQD11)+1 种基金the Locality-University Cooperation Project of Yantai City(No.2019XDRHXMPT18)the Ability Establishment of Sustainable Use for Valuable Chinese Medicine Resources(No.2060302)。
文摘Chlorogenic acid(5-CQA),neochlorogenic acid(3-CQA),and cryptochlorogenic acid(4-CQA),usually simultaneously exist in many traditional Chinese medicines(TCMs).However,insufficient attentions have been paid to the comparative metabolism study on these three isomeric constituents with similar effects on anti-inflammation until now.In this study,a novel strategy was established to perform comparative analysis of their metabolic fates in rats and elucidate the pharmacological mechanism of antiinflammation.Firstly,diagnostic product ions(DPIs)deduced from the representative reference standards were adopted to rapidly screen and characterize the metabolites in rat plasma,urine and faeces using UHPLC-Q-TOF MS.Subsequently,Network pharmacology was utilized to elucidate their anti-inflammatory mechanism.Consequently,a total of 73 metabolites were detected and characterized,including 50,47 and 43 metabolites for 5-CQA,4-CQA and 3-CQA,orderly.Moreover,the network pharmacology study indicated that these three isomeric constituents and their major metabolites with similar in vivo metabolic pathways exerted anti-inflammatory effects through co-owned 20 biological processes,which involved 10 major signal pathways and 159 potential targets.Our study shed light on the similarities and differences of the metabolic profiling and anti-inflammatory activity among these three isomeric constituents and set an example for the further researches on the active mechanism of isomeric constituents existing in TCMs based on comparative metabolism study.
基金supported by the Shanghai Pu-Jiang Grant, the National Natural Science Foundation of China (Grant Nos. 10875077 and 11075103)the Doctoral Program of High Education Science Foundation (Grant No.20090073110061)the Chinese Major State Basic Research Development Program (Grant No. 2007CB815005)
文摘Recent fission experiment data provide interesting structure information for neutron-rich nuclei in the mass A ～ 160 region. We apply the projected shell model to study the strongly-deformed, neutron-rich Sm isotopes. We perform calculations for rotational bands up to spin I = 20 (29/2) for even-even (odd-neutron) Sm isotopes, and analyze the band structure of low-lying states with quasiparticle excitations. Emphasis is given to rotational bands based on one-quasiparticle (1-qp) configurations in the odd-mass 159Sm. The 159 Sm result is discussed together with those of the even-even isotopes 158,160Sm. New bands in 159Sm based on neutron 1-qp 1/2 and 5/2+ configurations are predicted. Electromagnetic transition probabilities are discussed.
文摘The concentrations of 16 polycyclic aromatic hydrocarbons（PAHs） were determined in surface sediment samples from nine sites located at the Iguau River Basin in the Metropolitan Region of Curitiba,Brazil to evaluate their distribution and sources.The total concentration of the PAHs was greater for sediments from highly urbanized areas,while the sediments from the Iraí Environmental Protection Area（Iraí EPA） showed significantly low concentrations.The sediments from the Iguau and Barigui rivers were classified as highly contaminated,while those from the Cercado and Curralinho rivers were classified as moderately contaminated.The predominance of PAHs containing two to four aromatic rings in most of the samples suggested the direct input of raw sewage into the water resources evaluated.Benzo[g,h,i]perylene,dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene were predominant in sediments from the areas under the greatest urban and industrial development.The correlation between thermodynamic stability and the kinetics of evolution presented by the isomeric pairs indicated that combustion is the predominant source of PAHs in the sediments because the combustion of fossil fuels affected most of the points evaluated,followed by combustion of biomass and eventually combustion of oil product inputs.In general,the results showed that areas under strong urban influence,as well as the Iraí EPA,receive contributions of PAHs from similar sources.
基金Supported by National Natural Science Foundation of China(No.21136007,No.51302184)the National Research Fund for Fundamental Key Projects(No.2014CB260402)
文摘Two isomeric metal-organic frameworks(MOFs) with 2-dimensional(2D) and 3-dimensional(3D) topologies both comprised of Cu(Ⅱ) and OTf(OTf = trifluoromethanesulfonate) ions were synthesized and characterized.The CO_2,CH_4 and N_2 adsorption properties of the two isomeric MOFs were investigated from 263 K to 298 K at0.1 MPa.The results showed that the 2D MOF exhibited a higher selectivity for CO_2 from CO_2/CH_4 and CH_4from CH_4/N_2 compared to the 3D MOF,even though it possessed a lower surface area and pore volume.The higher adsorption heats of gases on the 2D MOF inferred the strong adsorption potential energy in the layered MOFs.Dynamic separation experiments using CO_2/CH_4 and CH_4/N_2 mixtures on the two MOFs proved that the2 D MOF had a longer elution time than the 3D MOF as well as better separation abilities.
基金the National Science Fund for Distinguished Young Scholars of China(no.21725404)Shanghai Scientific and Technological Innovation Project(18JC1410600)the Strategic Priority Research Program of the Chinese Academy of Sciences(grant no.XDB20000000)for financial support.
文摘Isomerism is an essential and widespread phenomenon in organic chemistry but rarely observed in covalent organic frameworks(COFs),a novel class of crystalline porous organic polymers with versatile applications.Herein,we give an account of the first example of a controllable synthesis of constitutional isomers of a COF.The two isomers exhibited marked differences in their gas/vapor adsorption behaviors and chemical stability in various solvents.Furthermore,structure transformation from one isomer to the other was realized.This work not only paves the way for rational design and synthesis of COF isomers but also provides a vivid example of structure–property relationship in crystalline porous polymers.
文摘The ^(nat)Mo(γ,xnp)^(95m,g)Nb photonuclear reaction was studied using the electron beam from the NSC KIPT linear accelerator LUE-40.The experiment was performed using the activation and off-line γ-ray spectrometric technique.The experimental isomeric yield ratio(IR) was determined for the reaction products ^(95m,g)Nb at the bremsstrahlung end-point energy E_(γmax) range of 38-93 MeV.The obtained values of IR are in satisfactory agreement with the results of other studies and extend the range of previously known data.The theoretical values of the yields Y_(m,g)(E_(γmax)) and the IR for the isomeric pair ^(95m,g)Nb from the ^(nat)Mo(γ,xnp) reaction were calculated using the partial cross-sections σ(E) from the TALYS1.95 code for six different level density models.For the investigated range of E_(γmax),the theoretical dependence of IR on energy was confirmed-the IR smoothly increases with increasing energy.The comparison showed a noticeable difference(more than 3.85 times) in the experimental IR relative to all theoretical estimates.
基金financially supported by the Ministry of Science and Technology of China (No. 2014CB643501)the National Natural Science Foundation of China (Nos. 21634004 and 51403070)+1 种基金the Foundation of Guangzhou Science and Technology Project (No. 201707020019)Zhi-Cheng Hu thanks the financial support from China Postdoctoral Science Foundation (No. 2017M622684)
文摘We present here a series of perylene diimide(PDI)based isomeric conjugated polymers for the application as efficient electron acceptors in all-polymer solar cells(all-PSCs).By copolymerizing PDI monomers with 1,4-diethynylbenzene(para-linkage)and 1,3-diethynylbenzene(meta-linkage),isomeric PDI based conjugated polymers with parallel and non-parallel PDI units inside backbones were obtained.It was found that para-linked conjugated polymer(PA)showed better solubility,strongerπ-πstacking,more favorable blend morphology,and better photovoltaic performance than those of meta-linked conjugated polymers(PM)did.Device based on PTB7-Th:PA(PTB7-Th:poly{4,8-bis[5-(2-ethylhexyl)-thiophen-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophene-4,6-diyl})showed significantly enhanced photovoltaic performance than that of PTB7-Th:MA(3.29%versus 0.92%).Moreover,the photovoltaic performance of these polymeric acceptors could be further improved via a terpolymeric strategy.By copolymerizing a small amount of meta-linkages into PA,the optimized terpolymeric acceptors enabled to enhance photovoltaic performance with improved the short-circuit current density(Jsc)and fill factor(FF),resulting in an improved power conversion efficiency(PCE)of 4.03%.
基金gratitude to the team of the LINAC-200 electron accelerator and the management of the Joint Institute for Nuclear Research for their support in conducting the experiments。
文摘The yields of photonuclear reactions in the 107Ag,113In,and 115In nuclei were measured.Monte Carlo simulations were performed using the Geant4 code,and the results were compared with the experimental values.The isomeric ratios of the yields in the reactions 107Ag(γ,n)106m,gAg and 113In(γ,m)112m,gIn were determined,and the cross sections for the reactions 107Ag(γ,n)106gAg and 107Ag(γ,2n)105Ag at an energy of 20 MeV were calculated based on the experimental data.
基金supported by the Youth Science Foundation of Jining University(2009QNKJ07)
文摘Two new isomeric Au complexes, Au（PPh3）（bmt）, have been synthesized via the reaction of Au（PPh3）CI with 2-benzimidazolethiol （Hbmt） in dichloromethane （CH2Cl2） solution. Their crystal structures were determined by elemental analysis and single-crystal X-ray diffraction studies. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 19.589（2）, b = 21.1368（15）, c = 23.424（2） A, β = 108.346（4）°, V= 9206.1（14） A3, Mr = 1216.85, Dc = 1.756 g/cm3, μ = 6.566 mm^-1, F（000） = 4704, Z = 8, the final R = 0.0563 and wR = 0.1028 for 8125 reflections with I 〉 2σ（I）. Complex 2 crystallizes in the monoclinic system, space group P21/n with a = 9.627（3）, b = 21.384（8）, c = 22.308（8） A, β = 92.068（6）°, V= 4590（3） A3, Mr = 1216.85, Dc = 1.761 g/cms, μ = 6.585 mm^-1, F（000） = 2352, Z = 4, the final R = 0.0500 and wR = 0.0883 for 10477 reflections with I 〉 2σ（i）. X-ray diffraction studies reveal that complexes 1 and 2 both feature a 1D chain along the a axis.
文摘The chlorocarbenoid , CHCl2Li , was studied by means of ab initio molecular or- bital theory. Three equilibrium structures and two isomerization transition states were located. The calculations showed that the three-membered ring structure is the most stable. The 'classical tetrahedral' structure is not the local minimum on the potential energy surface.
基金Project supported by the National Natural Science Fundaion of China.
文摘The isomeric structures, isomerization and decomposition of silylenoids H(2)SiMX (MX=KF, KCl, LiBr, NaBr and KBr) have been investigated by ab initio molecular orbital theory. These silylenoids have four kinds of very similar equilibrium structures. The three-membered ring and p-complex structures should be stable and experimentally detectable. The lifetime of sigma-complex and tetrahedral structures would be very short and experimentally undetectable.
文摘An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly（α-methylstyrene）（PαMS） chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.
文摘Mixed symmetry states are studied in the framework of the neutron-proton interacting boson model. It is found that some of the mixed symmetry states with moderate high spins change very fast with respect to the Majorana interaction. Under certain conditions, they become the yrast state or yrare state. These states are difficult to decay and become very stable. This study suggests that a possible new mode of isomers may exist due to the special nature in their proton and neutron degrees of freedom.
基金supported by the National Natural science Foundation of China(Nos.11875016,12165006).
文摘A lead-shielded HPGe detector and offlineγ-ray spectra of the residual product were used to measure the cross section(CS)and ratios of isomeric CS(σm/σg)in^(134)Xe(n,2n)^(133m),gXe reactions at different energies(13.5 MeV,13.8 MeV,14.1 MeV,14.4 MeV,14.8 MeV)relative to the^(93)Nb(n,2n)^(92)mNb reaction CS.The target was high-purity natural Xe gas under high pressure.The T(d,n)4He reaction produces neutrons.TALYS code(version 1.95)for nuclear reactions was used for calculations,with default parameters and nuclear level density models.The uncertainties in the measured CS data were thoroughly analyzed using the covariance analysis method.The results were compared with theoretical values,evaluation data,and previous experimental findings.CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5 MeV,13.8 MeV,and 14.1 MeV neutron energies are reported for the first time.This research advances our knowledge of pre-equilibrium emission in the(n,2n)reaction channel by resolving inconsistencies in the Xe data.
文摘A new value for the emission probability of 137.144 keV γ-rays from 186gRe decay is recommended to be （9.47±0.03）/%. Using this value the measured cross sections for 187Re（n,2n）186mRe and 187Re（n,2n）186gRe reactions around 14 MeV are analyzed, and the cross section for187Ke（n,2n）186m＋gRe reaction at 14.g MeV is （2213=k116） mb. The UNF code was adopted to calculate the cross sections for the 187Re（n,2n）186m＋gRe reaction below 20 MeV, fitting to the value （2213±116） mb at 14.8 MeV using a set of optimum neutron optical potential parameters which were obtained based on the relevant experimental data of rhenium. The isomeric cross section ratio for the 187Re（n,2n）186m,gRe reaction was analyzed using the V-H method based on nuclear statistical theory. Combining these calculated results, the excitation functions for the 187Re（n,2n）lS6mRe and 187Re（n,2n）186gRe reactions were obtained. The obtained results are in good agreement with the available experimental data.
